Image transmitting tube



Oct. 14, 1941. H. NELSON IMAGE TRANSMITTING TUBE Filed Jan. 51, 1959 2Sheets-Sheet l mm MN l m IT T m B A TTORNEY.

Oct. 14, 1941. H. NELSON 2,258,791

IMAGE TRANMITTING TUBE Filed Jan. 31, 1939 2 Sheets-Sheet 2 7'0 VERT/CAL SAW 7'0077/ GENERATOR INVEN TOR. HERBERT NELSON A TTORN E Y.

Patented Oct. 14, 1941 mesne assignments, to Radio Corporation of.America, New York, N. Y., a corporation of Delaware 12 Claims.

a-My invention relates to electronic devices and is concerned primarilywith television transmit ting tubes and a new method for generatingtelevision signals representative of an optical image whichx'may berecreated asa replica of the. image at a distance.

' sIn:electronic image'transmitting tubes of the stora'ge'type it hasbeen found that in'many instances the signal to noise ratio is notas-high ast 'might' be desired for the transmission of imageshaving'lowvalues of light intensity. It is 'well known that theeifective'sensitivit'y of sucha tube with a mosaic type electrode'islimited by the absence of a material electric field for drawingtheemitted electrons away from the mosaic 'of=photosensitive. particles andby the factthat' inost'of "the secondary electrons produced bytheimpi'ng'ement of the scanning beam on the surface of the mosaicreturn to the mosaic. Since the secondary electrons return to th mosaleat random,'local potential distributions are formedion the mosaic whichresult in a spurious signal, usually referred to in. the art as darkspot signal, which introduces distortion and dark spot effects. in therecreated optical image.

Q'It'is an object of my invention to provide alight translating andscanning device which will convert optical efiects into signallingimpulses and :simultaneously provide a response whichis proportional tothe optical effects for which translation is desired without theintroduction-Tof'ldistortion such as dark spot effects.

Application January 31, 1939, Serial No. 253,763

ondary electrons upon being scanned by an elec; tron beam the saidsecondary"ele'ctronsbeing diverted .from' the mosaic electrode -along'defi nite paths thereby preventing their return to the mosaicelectrode, and'neutraliziiigithe' residuary charge produced on themosaic enctrode in accordance with the scanning operation by. subjectingthe mosaic to electronicenergy'i'n a time and spacesequence following:thatot the scanning operation. Further in accordance with my invention,I selectively collect the electrons, both primary photoelectrons andsecondary electrons, in'accordanc'e with the potential at their pointsof origin and also in accordance 'with their relative initialvelocities, by providing crossed electromagnetic and electrostaticfields whereby high velocity electrons will be collected in one circuitwhere they may be utiliiedto generate television signals and lowvelocity el'e'ctrons Will be rejectedby that circuit. Still otherobjects, features and advantages of my invention will become apparentand will at once suggest themselves tothose skilled in the art to whichthe, invention'is directed from the follow- Another object. ofniyinvention is to provide selective means in and a method of operationora television transmitting tube whereby only the energy representativeof the signal energy isutilized and the non-signal energy is excluded.It is a further object of my invention to provide an image translatingdevice having a minimum of spurious effects which produce distortion ofthe recreated replica of an image to be transmitted, and a still furtherobject to provide means whereby a more sensitive photoelectric structuremay be utilized to the fullest an intensity'corresponding to the opticalimage intensity and distribution which electrostatic image is used ,tocontrolthe liberation of sec-' ing description" taken in connection withcompanying drawings in which: 1 c

Figure 1 is a longitudinal perspective view, partially in section, of anelectron discharge device, embodying my invention, and a diagram of theassociated circuits;

Figure 2 is a plan view of the device shown in Figure 1, showing themagnetic field generator used therewith; and,

Figure 3 is a schematic representation of a portion of the electrodestructure shown'in Figure 1 to show the operation of the device,

In the illustrative'embodiment "of my invention as shown in Figure 1,the discharge device or cathode ray tube comprises a highly evacuatedglass envelope or bulb l of cylindricalshape with a tubular arm or necksection enclosing a conventional type electron gun. The bulb l enclosesa fiat target or mosaic electrode 2 opposite the junction of the necksection with the cylindrical section so that the surfaceqof the mosaicelectrode 2 may be scanned by an electron beam from the electron gunlocated in the neck section. Since the image projected on the mosaicelectrode is produced by light from' an object situated outside thetube, a portion of the tube such as the transparent window 3 which isoptically uniform and preferably a continuation of the cylindricalportion of the envelope I, is provided so that the image of which anelec-' rical replic'ais to-be transmitted may be'pro the" ac- .iectedupon the mosaic electrode 2 with a minimum of distortion by a lenssystem 4.

The electron gun assembly is of the conventional type and comprises acathode from which an electron stream may be drawn, a control electrode6 connected to the usual biasing battery, and a first anode I maintainedpositive with respect to the cathode 5. The electron stream leaving thefirst anode I is accelerated and concentrated into an electron scanningbeam focused on the surface of the target or mosaic electrode 2 facingthe electron gun by a second anode 8 which is preferably a conductivecoating on a portion of the inner surface of the necksection of the bulbI. The beam is preferably focused to a small spot having a cross-sectionat the mosaic electrode equivalent to the elemental area of the image tobe transmitted. The first anode I and the second anode 8 are maintainedat the desired positive potentials with respect to the cathode by apotential source such as the battery 9. Conventional deflection means,such as the deflection coils I I) and Il, may be energized withsaw-tooth currents to sweep the beam in mutually perpendiculardirections to scan the mosaicelectrode 2. Thus the coils I 0 aredesigned to operate at relatively low frequency for frame scanning suchas 30 cycles per second while the coils I I are designed to operate atrelatively high frequency for line scanning. The line scanning frequencyfor 30 frames per second and 441 lines would thus be 13,230 cycles persecond. It is obvious that conventional electrostatic deflection platesor electrodes may be substituted for either one or both of thedeflection coils if desired.

The mosaic electrode 2 is of the conventional type and comprises a layerI2 of insulating material having on the side facing the electron gun amosaic consisting of a multiplicity of mutually separated silverparticles I3 which are oxidized and coated with caesium or other alkalimetal to provide a mosaic surface of high photosensitivity whichexhibits high secondary electron emission when scanned by the electronbeam from the electron gun. The insulating layer I2 may be depositeddirectly on a metal base M or it may be a sheet of insulation such asmica. I have found it desirable that the insulating layer I2 extend onlyover the central portion of the metal base I4 so that the base extendsbeyond the borders of the insulation and the mosaic of photosensitiveparticles thereon for a distance of approximately one quarter inch. Themetal base l4 serves as a common condenser plate, the other plate beingsubdivided into a great number of individual plates and constituted bythe particles I3. The construction and photosensitization of suchelectrodes is well known in the art and is more adequately described byS. F. Essig in U. S. Patent 2,065,570.

In accordance with my invention I project an optical image on the mosaicelectrode to liberate photoelectrons and form thereby an electrostaticimage of the optical image and scan the mosaic electrode with a beam ofhigh velocity electrons to generate an electron flow representative ofthe optical image projected on the mosaic electrode and direct thiselectron flow away from the surface of the mosaic. During the scanningwith high velocity electrons a residuary charge is formed on the mosaicparticles which I neutralize by sweeping a broad sheet-like beam ofelectrons over the mosaic closely following the scanning beam. To sweepthe sheet-like beam and remove the electron flow generated on the mosaicelectrode from the surface of the electrode I provide adjacent themosaic electrode crossed magnetic and electrostatic fields. Further inaccordance with the invention I utilize the crossed magnetic andelectrostatic fields to direct the signal electrons to a signalelectrode where they may be utilized and the non-signal electrons to aposition at which they may be rejected.

Referring again to Figure 1, I provide at one side of the mosaicelectrode 2 and preferably in a plane coplanar therewith an aperturedbeam focusing electrode I5 which is preferably of somewhat greaterlength than the width of the mosaic along the tube axis. The electrode I5 is provided with an elongated aperture or slot I6 parallel with oneedge of the mosaic electrode 2 and preferably coplanar with the mosaicelectrode. On the side of the slot I6 opposite that facing the electrongun, I provide an electron source preferably of somewhat greater lengththan the length of the aperture I6. This electron source may take theform of a uni-potential cathode I! having an electron emitting surfaceor coating [8 of alkaline earth oxides which when heated such as by theheater I9 emits a sheet-like beam of low velocity electrons. Thesheet-like beam of electrons is directed toward and is collected in mostpart on the mosaic electrode by crossed magnetic and electrostaticfields generated in a manner as described below. It is obvious that theunipotential cathode may be replaced by any other electron source suchas a directly heated cathode.

The low velocity electrons liberated by the high velocity beam impingingon the mosaic electrode, the electrons from the cathode I! which are notcollected by the mosaic and the photoelectrons liberated from the mosaicunder the influence of the optical image may be collected immediatelyadjacent the edge of the mosaic electrode opposite the cathode I1 andutilized to produce picture signals without dark spot distortion but Iprefer to increase the signal to noise ratio by collecting only thesecondary electrons liberated from the mosaic surface under scansion bythe high velocity beam which are liberated from the elemental areas inaccordance with the intensity of the optical image on the respectiveareas. I therefore provide beyond the edge of the mosaic electrodeopposite that edge which is adjacent the beam forming electrode I5 asignal electrode 23 preferably in the same plane as the electrode I5 andthe mosaic electrode 2. The electrode 23 collects electrons originatingfrom points which are negative with respect to it, such as the secondaryelectrons from the mosaic surface, but rejects electrons having lowinitial velocities which originate from points which are positive withrespect to it, such as the photoelectrons and electrons from the cathodeIT. The electrons rejected by the electrode 23 are collected by acollecting electrode 24 which is preferably perpendicular to the commonplane of the electrode system I5, 2 and 23 and located near but slightlyspaced from the end of the electrode 23 opposite the end adjoining theedge of the mosaic electrode 2. In addition to the above describedsystem of electrodes I provide an electrostatic accelerating electrode25 which is preferably in a plane parallel with the common planes of theelectrodes I5, 2 and 23 but spaced a substantial distance therefrom.While I have shown the electrode 25 as being constructed from a singlemagnetic field strength-varying betweenand metal'sheet-itis'obviousthatiseveral electrically connected. electrodes having. an.equivalent area cblfldibe azused so .I prefer .to' refer to this. orthese electrodes as a second system of electrodes to differentiateoverthe firsttsys'tem which includes the. electrodes I5, 2and 23;Furthermore, while I have shown the electrode. 25 as being formedintegrally with the electrode 24 these electrodes may be separate anddistinct and may be connectedutogether outside of the bulb 1. Therefore,when I refer to theelectron collecting electrode I mean to refer to anelectrode having the. property-of collecting electrons and in aposition-where it. will intercept the electrons to be collected such asthe electrode 24 which is at the end of the two electrode systemsopposite-the endnear the elongated cathode H. A portion of thisaccelerating electrode 25 is between the mosaicelectrode 2 and theelectron gun in the neck section of the bulb so that I provide in theelectrode=25 between thegunand the mosaic electrade an' opening 26,preferably rectangular, through which. the optical image to be transmitted may be projected on'the mosaic electrode and the :mosaic'electrode scanned by the high velocityele'ct'ron beam from the-gun.Located in a'planer substantially midway between the electrodes"l5,.'2and 23 and the deflection electrode 25.1 provide an equalizing electrode21 which is for the purpose of equalizing and maintaining moreuniformthe electrostatic field between these electrodes during operation. Theequalizing electrode 21 is preferably a U shaped metal plate, thecentral portion of which is open to allow unimpeded the electron flowalong the length of ,theelectr'ode structure. I

To provide the crossed electrostatic-magnetic fields referred to above,I have found it convenof force parallel withiand' transverse to theelectrodes 2,- I5, 23 and 25, in the: direction shown by the arrow 28.For this purpose I have found suitable a magnetic yoke arrangement shownin .Figure 2 including pole faces 29 and an inter- 'netic fieldv may beproduced,-v the field extending over the length of the tube andpreferably slightly'beyond the above mentioned electrode'structures; Inaddition to the'coilF 3! which produces uniform magnetic flux betweenthe pole faces 29, -I provide an auxiliary coil 34 likewise surroundingthe yoke 30', the said coil being ener 4 lent to provide magnetic meansoutside of the bulb] to produce a magnetic field having lines volts andground such as'approxi'mately' 25 volts gized froma source 35 ofsawtooth current, the

frequency of which is determined by the number of frames which it isdesired to scan per second. Thus, if the frame scannin coils H! aresupplied with 30 cycle per second sawtooth cur-\ rents I likewise'applythe same frequency of sawtooth currents to the coil 34'. The purpose of'the coil 34 is to produce a varying magnetic field to sweep thesheet-like beam from the oathode I! over the mosaic electrode in a spaceand time sequence closely following the vertical scanhing-of the highVelocity beam. I have found in practice that a constant and uniformmagnetic I field density'between the polefac'es 29 'of 6.1

gauses is satisfactory forthe voltage ratings of "the tube tobedisclosedbelow and thataivariable V 3 7-5 the electrodes in thedirection of the arrow28ggausesadded .to the co'nstant magnetic; fieldis sufiicient'in following my method of operation.

Thelvalue of theconstantuniformfield required K=11.3, V=potentialbetween electrodes volts, v D=dis'tance between l4 'and'25 incentimeters, d=distance betweentaperture l6 and the more distantparallel edge of electrofie fl! centimeters.

The value of "the varying umrormndd -required may be 'eiipressed as theconstant field niinu's'a quantity determined by the above formula but Isubstituting a for whered'fidistaricebetween aperture l6 andthe nearestparallel edge trode lfl in'centimterslfl i A Thetubeshown in Figure 1ie-made ready for operation by applying appropriate electron beamaccelerating potentials to the electron gunam odes l and 8 with respecttothe cathode 5 such as by the potential {source or battery 9; 'Thepotential between the anode 8 andthe cathode 5' is preferablyapproximatel'y'lOOQ volts, the po tential on the anode 'i 'being variedto p'rod'u'ce an electron beamfocused on the front surface of the mosaicelectrode 2. The anode aispree erably operated at approximately '75volts and the accelerating electrode 25- at' approximately 50 Volts bothof these values being positive witnes spect to ground. "The beam formingelectrode I5 is conhected'to ground through the potential source orbattery 36 so that it is maintained between I to e volts positive withrespect to ground. The cathode l'l is also connectedto ground throughthe potential source or battery 31 so that it'is maintained between 0 to3 volts positive with respect to ground Ihe' mosaic "electrode base Itis connected directly to ground although I havefound the tube to operatesati's electrode'23, which ccllec'tsjthesecondary elect-L tronstoproduce the'sig'nalliiig energyjiscon-f nected tothe input circuit ofa tra'n's'latingdeg vice such as the thermionic tube "38, andto groundthrough'the'output inipedanc'sa. jF'or these conditions the U shapedequalizing -'elec trodeZ'l is operated at a potential between 50 tomaintain uniform the electrostatic fieldbe tween'the elec'trodes 2. l5and 23 and the a'ccelfcrating electrode 25;- The aboye potentials havebeenfound suitable for a tube wherein the conibined length of theelectrodes I5, 2 and 23-incl uding the spacing 'tnereb'etween is 12inches, the distancebetweentlie' plane of the electrodes 2. l5 and 23and. the plane of the emu-Od r; 1

beihg 1% inches; the length of the beam form ing electrode l5 being 3inches, thatlof thesigi nal electrode 2-3 being 6 inches, the width ofthe The width of the electrodes and the length 'of the mosaicelectrode,fthat is the dimension of should be uniform but the abovedimensions are not critical, although the ratio of dimensions of theelectrodes to the other electrodes should be maintained. Thus theelectrodes should be designed so as to meet the requirements entailed bythe necessary paths of both the electrons flowing from the cathode H tothe mosaic electrode and the electrons flowing from the mosaic electrodeto the rejection electrode 23 and the collecting electrode 24.

After the tube is made ready for operation by the application ofsuitable operating potentials an optical image of an object of which apicture is to be transmitted is focused on the front surface of themosaic electrode 2 to produce thereon an electrostatic imagecorresponding in elemental potential distribution to the optical image.This electrostatic image is formed by the liberation of photoelectronsfrom the front surface of the'mosaic electrode in accordance with theintensity of the optical image. These photoelectrons have relatively lowvelocity and by their liberation from the mosaic surface produce anelectrostatic image of positive electrostatic charges on the mosaicelectrode. These photoelectrons are directed toward the signal electrode23 and the collecting electrode 24 by the crossed magnetic andelectrostatic fields generated by the potential differences between theaccelerating electrode 25 and electrodes [5, 2 and 23 and by the coils39 and 3!. Due to the low velocity of these electrons they fail toimpinge upon the signal electrode 23 but continue to and are collectedby the collecting electrode 2 Simultaneously with the projection of theoptical image upon the mosaic electrode, this electrode is scanned bythe electron beam from the electron gun, the line scanning being made tofollow paths substantially parallel with the aperture l6 and the cathodeI7. The electrons of the beam are of high velocity and liberatesecondary electrons from the particles l3 of the mosaic, the quantity ofthese electrons and the velocity thereof being proportional to theintensity of the electrostatic charge on the various particles. Thesesecondary electrons are directed by the crossed magnetic andelectrostatic fields toward the signal electrode 23, those havingsuincient velocity being collected by the electrode 23, those havinginsufiicient velocity being redirected and collected by the electrode24. In this manner the quantity of electrons reaching the electrode 23and consequently the signal produced across the output impedance 39 andapplied to the translation device or tube 33 is proportional to theintensity of the optical image being projected on the mosaic electrodeand is produced in a time sequence determined by the rate of scanning ofthe electron beam from the gun structure. Simultaneously with, butslightly following in time and space sequence the scanning of the mosaicelectrode by the high velocity beam the electrons from the broad beamoriginating at the cathode I! are swept'in one direction only, that is,in a direction perpendicular to the longitudinal dimension of the slot56 across the mosaic electrode by the varying magnetic field produced bythe frame sawtooth currents applied to the coil 3|. The electrons fromthe broad beam impinge on the mosaic electrode at a very low velocitysince the only voltage difference between the electrode 23 and themosaic electrode 2 is that occasioned by the positive charge or chargeson the particles I 3 as a result of secondary emission from theseparticles under bombardment by the high velocity beam. The electronsfrom the broad beam therefore neutralize these positive charges andcharge the particles l3 negatively with respect to the base I 4 on theopposite side of the mosaic electrode so that they are again incondition to liberate photoelectrons in response to the optical imagefocused thereon.

This mode of operation may be explained more fully by reference toFigure 3 which shows the approximate paths of the electrons during theoperation of the device shown in Figure 1. Under the influence of theoptical image, electrons are liberated from the particles I3 of themosaic electrode and proceed toward the electrode 23 along a path suchas represented by the dashed line 49 but are repelled due to their lowvelocity by the electrode 23 and continue to the electrode 24 where theyare collected. The dashed line H represents the path of the electronsfrom the electron gun which impinge on the'particles I3 of the mosaicliberating secondary electrons which follow the path shown by the dashedline 42 to the signal electrode 23. Certain of these secondary electronsfollowing the path shown by the dashed line 40 may be repelled if theyare of very low velocity whereupon they follow a path to the electrode24 such as shown by the dashed line 43. The secondary electrons flowingalong the path shown by the dashed line 42 and collected by the signalelectrode 23 flow to ground through the impedance 39 thereby producingvoltage variations in a time sequence determined by the scanning andrepresentative of the intensity of the optical image from point to pointover the area of the mosaic electrode. These voltage variations areapplied to the input circuit of the translation device or tube 38 toproduce the television signals which are further amplified andtransmitted as well known in the art. The electrostatic residuary chargeon the mosaic is neutralized by the electrons from the cathode llflowing along the path shown in Figure 3 by the dashed line 44, thosewhich are not collected by the mosaic following the path 45 to thecollector electrode 2:1, since they are of very low velocity. Since onlythe secondary electrons flowing along the path 62 are collected by thesignal electrode the signal to noise ratio of the device is increased,the electrons which would tend to increase distortion and noise beingcollected by the electrode 24 where they are discarded.

It will be seen from the examination of the above description anddescribed operation of my invention that I have provided a device anddisclosed a method of generating television signals which will convertoptical effects into signalling impulses and simultaneously provide aresponse which is proportional to the optical effects for whichtranslation is desired and at the same time that I have provided meanswhereby the energy representative of the signal energy is utilized tothe exclusion of non-signal energy. Since the secondary electronsliberated from the surface of the mosaic electrode are prevented fromreturning to this surface by the crossed magnetic and electrostaticfields, there is no possibility of spurious effects such as dark spotsig nals being produced which would distort the recreated replica of theimage being transmitted While I have indicated the preferred embodimentsof my invention of which I am now aware and have also indicated only onespecific application for which my invention may be employed, it will beapparent that my invention is by no means limited to the exact formsillustrated or the use indicated, but that many variations may be madein the particular structure used and the purpose 'forwhich it isemployed without departing from the' scope of my invention as set forthin the appended claims.

- 'I claim: 7

- '11.. A 1 television transmitting tube comprisin an evacuatedenvelope, a light sensitive mosaic electrode having the property ofliberating elec:- trons when scanned by a high velocity electron beampositioned in aid envelope to have focused thereon an optical image, anelectron gun exposed to said mosaic electrode to generate and directarbeam of electrons on said electrode, means to scan the beam from saidgun over said mosaic in two mutually perpendicular directions,anelongated cathode parallel to one of said directions of scanning andhaving a length substantially equal to the dimension of said mosaicelectrode in the "direction of said one of said directions of scan.-ning to "generate a sheet-like beam of electrons said cathode lying insubstantially the same plane as the: plane of said mosaic lectrode,magnetic means to sweep said sheets-like beam along arced path ofprogressively increasing length over said mosaic electrodein a timeand'space sequence following the scanning of thebeam of electrons fromsaidgun and means to collect electrons liberated from the surface ofsaid mosaic electrode.

' 2., A television transmitting tube comprising an electrode arrangementincluding two elongated systems of mutually parallel flat extendedelectrodes, a mosaic of mutually separated photosensitive particlessubstantially in the plane of one system and between two electrodes ofthat system to liberate primary electrons in response to .an opticalimage 'focused thereon, an elongated cathode exposed to said mosaic,substantially pers pendicular' to the, longitudinal dimension of saidelectrodes, and'adjacent one end of the said one system of electrodes togenerate a flat beam of primary electrons, an electron collectingelectrode substantially closing the space between the two systems at theopposite end of said electrodes from'said cathode, an electron gunexposed to said mosaic ;of photosensitive particles to generateand-focus an electron beam of highwelocity electrons pthereon, meanstoscan said beam over said'mosaic in two mutually perpendicular direcetions on of which is substantially parallel to said elongated cathode toliberate secondary electrons fromthe scanned area of saidmosaic, andmeans to generate a magnetic field of varying intensity between the twosystems of electrodes to direct the electrons from said elongatedcathode and from said mosaic electrode along arced paths toward saidcollecting electrode and to separate said secendary'electrons from saidprimary elec: trons.

3. A cathode ray television transmitting device having an evacuatedenvelope, a mosaic electrode within the envelope, elongated electrodemeans extendingin planes parallel with and beyond two opposite edges ofsaid mosaic electrode by an amountigreater'than the width of said mosaicelectrode between the said two edges to generate a substantially uniformelectrostatic field over the silrface'of said mosaic electrode andbeyond the said two-edges thereof, an elongated primary electronemitting cathode near one end of said electrode means having itslongitudinal dimension parallel with said edges,- anelectron collectingelectrode adjacent the opposite end of said lec. trode means,,,anelectron gun exposed to said mosaic electrode ,to generate and focus anelec-.

,e saris? compris n anenro ooa am saio oloo odo oi on: tended area insaid envelope, a first electrod the plane of said mosaic electrode d I gon ud nally o the enve o erom adiaooh lo d e o th mosai e t ode asooonol. ol o oo o in th p ans o s id mosaic electro e o in the. opposte. dir ct on, from tho also saic t de o osi e h a, ed e, a e e tronsour e o onion-d li loh h 11 4 al sl wit the so -d ed es of a d lnoolootr do to p oduce a a b am of e e trons als ,9 s n to prod e an,elootron' sam' nhll nos n -hea ele onlson ool on sand deli-onions sedanpa a e n sub ta tially QQ XPF' P Y? with: said fi st and e ond o ootrdesan shaooo ther irom an to g n ra a su stantial oh iohnma r n ti fi de wee said de ecti electr de and a d othe e i ooosaho me ns to gen ratea iab e ma netic field so soah a d bro beam o lect on one ohrso zion oer said mosaic, lse

trode. V V

on o tho s ra te evision transm ttin 91sec? com i an en elo an e on atednoo so oh Jo n d to aid ome on .v ln sn o alon s de said en e o p os esold noel; n pai of plate s aped le tr des in nbstan ,ll tho s mo p a aan lyin djace t o posit e es o sa mosaic el tr de nne h atod r nlnio oooiton at aha el tron hsa l allias n one o aid late sha d ele od s analotr n. son in. sa d oohssotion t oonoo a also tron b en o elemental oossooiion to soon sh ll boom o el mental se t on o o s iq .lnos ic eletrode n a ser es of inos suh t n y pa a lel to said elon at d-ele ronsou ce, means toxgons at a o oss ol moshetlowleotior tat re o hav n a vay n -ma ne component t soon said not electron beam over said nosaio elde, .7 l

6- A athod ra l sion ransmittin ,dovice comprising an evacuated@Ilvelope, an elon; sa e h oks o oh ine t said envelo e, a mosa c el otooo i aid n elope opposi sa hs hseob on a ai o plo s shaped elec rodes iub ant al he some lans a and sa as: iac n opp it d e o a d mosa c eectrode, an e on edapertureln one of'sai p ate 56,6:- t n sa d ap rturebein disposed in a direction normal to an axis through the center ofsaid electrodes and said mosaic electrode, an elongated electron sourceadjacent said aperture to project a flat beam of electrons through said:a'perture and toward said mosaic electrode, an electron deflectingelectrode parallel to but separated from said mosaic electrode and saidpair of electrodes and having a surface coextensive with said mosaic.electrode and said pair of electrodes for producing a substantiallyuniform electric field, an electron collector electrode adjacent the endof said pair of electrodes furthest removed from said elongated electronsource, an electron gun in said neck section to produce a high velocityelectron beam of elemental cross-section, means to scan said beam fromsaid electron gun over said mosaic electrode in a series of parallellines parallel with said elongated aperture to liberate secondaryelectrons from said mosaic electrode, and means to generate a magneticfield transverse to said electrodes and parallel with said elongatedslot to direct electrons from said elongated cathode to said mosaicelectrode, electrons from said mosaic electrode other than saidsecondary electrons to said collector electrode, and said secondaryelectrons to one of said plateshaped electrodes.

- -7. The method of generating signals for television transmissioncomprising the steps of projecting an optical image on a light sensitivemosaic surface, scanning the surface with a beam of electrons toliberate secondary electrons having'a velocity distribution determinedby the intensity of elemental areas of light and shade of the opticalimage projected on the mosaic surface, collecting at a surface otherthan said mosaic surface electrons liberated from said mosaic surfacewith relatively high velocities, simultaneously rejecting from saidother surface electrons liberated from said mosaic surface havingrelatively low velocities, collecting the electrons rejected from saidother surface at a position removed from said other surface and saidmosaic surface and utilizing the electrons liberated from said mgsa icsurface with relatively rh lgllllclocities to produce signallingimpulses.

8. The method of geenrating signals for television transmissioncomprising the steps of projecting an optical image on a light sensitivemosaic surface, scanning the surface with an electron beam to liberatefrom each instantaneously scanned area of said surface electrons hav inga velocity distribution determined by the intensity of elemental areasof light and shade of the optical image projected on the areas of themosaic,surface, simultaneously removing t e ele'c'tfdns liberated fromthe mosaic surface from the neighborhood of each area of the surface asscanned, directing the liberated electrons to areas remote from saidmosaic surface along definite paths, collecting at a surface other thansaid mosaic surface electrons liberated from said mosaic surface withrelatively high velocities, simultaneously rejecting from the collectingsurface electrons liberated from said mosaic surface having relativelylow velocities and utilizing only the electrons of relatively highvelocity to produce signalling impulses.

9. The method of generating signals for television transmissioncomprising the steps of liberating photoelectrons from a surface inresponse to elemental areas of light and shade of an optical imagefocused thereon, generating an electron beam of elemental area, scanningsaid beam over said surface along a series of parallel lines to liberatefrom said surface secondary electrons having a velocity proportional tothe intensity of the light on the elemental areas, scanning said surfacewith an elongated beam of electrons of a length equivalent to that ofthe said lines, selectively collecting the photoelectrons and secondaryelectrons on surfaces other than the mosaic surface in accordance withthe velocity of said electrons and utilizing only the collectedsecondary electrons to produce signalling impulses.

10. The method of producing signal energy in a tube wherein is containeda capacitor having a multiplicity of light sensitive conductive elementsspaced from a common electrode element by a dielectric and a signalcollector electrode connected with a load circuit which includes thesteps of illuminating the light sensitive elements of the capacitor torelease from the individual discrete areas thereof a flow ofphotoelectrons proportional to the activating light and to simultaneously develop between the illuminated elements and the commonelectrode electrostatic charges, developing a concentrated beam ofelectrons, directing the concentrated beam of electrons to traverse theindividual discrete light sensitive elements of the capacitor to releasetherefrom secondary electrons measurable in accordance With a magnitudeof the developed electrostatic charges, collecting the photoelectronsreleased under activating light independently of the signal electrodeand the connected load circuit, directing the released secondaryelectrons upon the signal electrode to energize the load circuittherefrom in accordance with the magnitude of the instantaneouslyreleased secondary electron flow, developing an elongated beam ofelectrons simultaneously with the development of the concentrated beamof electrons, directing the elongated beam of electrons upon the areasof the capacitor in time relationship and spacial positioning followingthe instantaneous area of impact of the concentrated electron beam toremove by impact upon the capacitor surface residual electrostaticcharges resulting from the release of secondary electrons from the saidsurface, and collecting the electrons remaining subsequent toneutralization independently of the load circuit.

11. In a television system wherein is incorporated an electron tubehaving a photosensitive mosaic electrode, the method of signalgeneration which includes the steps of illuminating the mosaic electrodeby the light of an optical image to produce electrostatic charges,scanning the mosaic electrode with a sharply focused high velocityelectron beam to release from the mosaic electrodesecondary electrons ofa quantity substantially representative of the magnitude of theelectrostatic charge at the area of the mosaic scanned, floodingpredetermined areas of the mosaic electrode with low velocity electronssubsequent to the scanning thereof by the high velocity electrons torestore equilibrium potentials at scanned areas of the mosaic electrode,directing the released secondary electrons along a first predeterminedpath, directing both the excess of said low velocity electrons notcollected by the mosaic and the photo-electrons released from the mosaicby the light of the optical image along a second path, collecting theelectrons directed along each of said paths and generating wave trainsof signalling energy solely in accordance with the secondary electronscollected at the termination of the first of said paths.

12. In a television system wherein is incorporated an electron tubehaving a photosensitive mosaic electrode, the method of signalgeneration which includes the steps of illuminating the mosaic electrodeby the light of an optical image to produce electrostatic charges overthe mosaic electrode, scanning the mosaic electrode with a sharplyfocused high velocity electron beam to release from the mosaic electrodesecondary electrons in substantial proportion to the magnitude of theelectrostatic charge at the scanned area of the mosaic, floodingpredetermined areas of the mosaic element with low velocity electronssubsequent to the scanning thereof by the high velocity electrons torestore equilibrium potentials at the scanned areas of the mosaicelectrode, collecting the secondary electrons released from the mosaicdue to high velocity scanning thereof and independently collecting boththe HERBERT NELSON.

